Re: [PATCH] Unwinder improvements.

[Michal Ludvig <mludvig at suse dot cz>]

Richard Henderson wrote:

> On Wed, May 07, 2003 at 03:49:11PM +0200, Michal Ludvig wrote:
>
> > the attached patch adds a new function _Unwind_GetGRAddr()' to the 
> > unwinder. Having it there is necessary when doing a backtrace from the 
> > application to prevent a segfault in _Unwind_GetGR if requesting unsaved 
> > register.
> >
> > OK to apply?
>
>
> No.  You've not given sufficient rationale for why this function
> would need to be exported.

The API in <unwind.h> offers a function _Unwind_GetGR(). If I'm printing 
a backtrace (eg. in a case of a program crash) using 
_Unwind_ForceUnwind() I may choose to print argument registers (on archs 
where function parameters are passed in registers) or even all 
registers. However trying to fetch any register value via 
_Unwind_GetGR() without knowing if it was saved or not will sooner or 
later lead to a segfault (see a comment in _Unwind_GetGR() :-).

So I need a way to determine if a given register was saved in the 
context or not and that's why I added _Unwind_GetGRAddr(). Of course it 
could have been _Unwind_IsGRValid() returning true or false, but 
returning the address itself (or zero if not saved) is IMHO harmless.

Or am I wrong?

Michal Ludvig